1. Field of the Invention
The present invention relates to a pipe joint for a quartz pipe (hereinafter, referred to as "quartz pipe joint") which can be used in a connection for a quartz tank of an apparatus for cleaning a silicon wafer and a chemical distribution system, or in a chemical distribution system of a semiconductor production line, a system relating to a liquid crystal device, etc.
An example of a pipe joint of this kind is a pipe joint disclosed in Japanese Patent Publication (Kokoku) No. HEI1-54,599. With reference to FIG. 12, the pipe joint 100 will be described. In the pipe joint 100, a nut 110 and a seal fastening ring 120 are fitted onto a synthetic resin tube 200 in this sequence, and an end 201 of the synthetic resin tube 200 is then inserted into a pipe receiving portion 131 of a joint body 130. The nut 110 is loosely threadedly connected with the joint body 130, and then tightly fastened so that the fastening ring 120 is clamped between a tapered pressing face 132 of the joint body 130 and the nut 110. The reference numeral 121 designates a tapered receiving face which corresponds to the pressing face 132 of the joint body 130. The receiving face 121 is formed on the fastening ring 120.
In the pipe joint 100, the fastening ring 120 clamped between the pressing face 132 of the joint body 130 and the nut 110 is deformed to reduce its diameter in opposition to the elasticity of the material of the fastening ring 120. The fastening ring 120 which is deformed to reduce its diameter in this way "bites" the synthetic resin tube 200, thereby preventing the synthetic resin tube 200 from slipping out from the pipe joint.
2. Description of the Prior Art
In the pipe joint 100 shown in FIG. 12, the fastening ring 120 performs the sealing function of sealing the connection of the pipe joint 100 and the synthetic resin tube 200 to eliminate leakage of fluid, and also preforms the slipping-out preventing function of tightly fastening the synthetic resin tube 200 to prevent it from slipping out from the pipe joint.
In the pipe joint 100 shown in FIG. 12, however, when the fluid pressure applied to the pipe joint during actual use exceeds a certain limit, the biting portion (fastening portion) of the synthetic resin tube 200 at which the fastening ring 120 "bites" is deformed so that the tube easily slips out from the pipe joint. In the case where the fluid temperature is high, whether or not the fluid pressure exceeds the limit, that portion of the synthetic resin tube 200 is softened so that the tube easily slips out from the pipe joint. As the bore diameter of the synthetic resin tube 200 is increased, the stress relaxation occurs more easily at that portion of the synthetic resin tube 200, resulting in the synthetic resin tube 200 easily slipping out from the pipe joint 100. Because of these disadvantages due to the fluid pressure, the fluid temperature, the bore diameter, etc., the application of the pipe joint 100 shown in FIG. 12 is restricted to a narrow range.
On the other hand, in a chemical distribution system used in an apparatus for cleaning a silicon wafer, a semiconductor production line, a system relating to a liquid crystal device, etc., pipes for distributing chemicals are required to have highly excellent chemical resistance properties, pressure tightness, heat resistance, and the like. From this point of view, quartz pipes are preferably used as a piping member. A quartz pipe has excellent chemical resistance, and properties that make it difficult to be adversely affected by a variation of fluid pressure or fluid temperature. When a quartz pipe is used in place of the synthetic resin tube 200 shown in FIG. 12, therefore, the stress relaxation due to the effects of fluid pressure, fluid temperature, the size of the bore diameter, etc. hardly occurs at the portion where the fastening ring 120 exerts a fastening force, thereby reducing the possibility that the quartz pipe is caused to easily slip out from the pipe joint 100 by such effects.
When a quartz pipe is used in place of the synthetic resin tube 200, however, there arises another problem as follows: A quartz pipe has a property that it is hard to deform to reduce its diameter. Even if the nut 110 is tightly fastened using a tool such as a spanner, therefore, the slipping-out preventing function of the fastening ring 120 is not improved proportionally to the increase in the fastening force.